function message() {
    var txt="";
    try {
        adddlert("Welcome guest!");
    } catch(err) {
        txt="本页有一个错误。\n\n";
        txt+="错误描述：" + err.message + "\n\n";
        txt+="点击确定继续。\n\n";
        alert(txt);
    }
    txt = "no error"
}